Hives are raised red bumps (welts) or splotches on the skin. They’re a type of swelling on the surface of your skin and happen when your body has an allergic reaction. Allergic reactions happen when your immune system comes in contact with an allergen. Allergens are proteins that are harmless to many people but cause an allergic reaction in sensitive people.
Hives are often very itchy, but you might also feel burning or stinging. They can be as small as a fingertip or as big as a dinner plate. The medical name for hives is urticaria.
Sometimes, the welts from hives join together to form larger areas called plaques. Hives tend to fade within 24 hours, although they may be noticeable for several days or longer.
Acute urticaria refers to hives that don’t last very long (less than six weeks). Chronic urticaria refers to hives that happen at least twice a week for more than six weeks.
Chronic, spontaneous urticaria is the name for chronic hives that don’t have an obvious cause. An older name for this condition is chronic idiopathic urticaria.
There’s also a condition called physical urticaria, or inducible urticaria. These hives might pop up when you’re in the cold, heat or sun. Some people react to vibrations or pressure, exercising or sweating. Physical hives usually appear within an hour after exposure. This type of hives can also be chronic.
A rash is a skin condition that involves something out of the ordinary, like spots, swelling, itchiness or redness. Hives is an example of a rash, but not all rashes are hives.
Anyone can get hives. If you’re someone who reacts to many types of allergens, you may get hives frequently. Other people who don’t react to allergens may get hives once or a few times in their lives.
There seems to be a relationship between acute hives and conditions like asthma, allergic rhinitis and atopic dermatitis, especially in children. You might also be affected by hives during periods of extreme stress.
Around 20% of the population will get hives at least one time. About 1% to 3% of the population has chronic hives.
Hives look different depending on the person and the situation. They can show up anywhere on your body. Signs of acute hives include:
In many respects, chronic hives and acute hives may look alike: they can be itchy, swollen raised welts that turn lighter in the center and with pressure. However, chronic hives can:
Acute hives are often an allergic reaction to something you put into your body, like food, drink or medication, or something that you touch. The skin has immune cells called mast cells. When these cells go into action, they release chemicals, including one called histamine. Histamine is the reason that hives form.
You can also get hives for a variety of other reasons. Some of these include having an infection, stress or physical pressure on your skin. It’s not uncommon for healthcare providers to be unable to determine exactly what caused your hives.
Unlike acute hives, chronic hives aren’t usually caused by allergies. They may be caused by infections from bacteria or viruses, or as a result of other medical conditions like lupus. Your provider may not discover an exact cause. In these cases, chronic hives are said to be idiopathic or spontaneous.
Chronic hives do last for long periods of time but usually aren’t permanent. They can be uncomfortable, but they aren’t life-threatening.
Unlike some other skin conditions, hives aren’t contagious. But if you develop hives because your skin is exposed to secretions from a plant like poison ivy, you can spread the allergenic plant product to others until you wash it off your skin.
Your healthcare provider can diagnose hives and angioedema by looking at your skin. Allergy tests can help identify what’s triggering a reaction, but this is true primarily for acute hives. Knowing the cause can help you avoid allergens and the hives that come with them. Allergy tests to diagnose hives include:
Most of the time, hives go away without treatment. Your healthcare provider might recommend medications and at-home care to help you feel better and lower your chances of having hives again. Treatments include:
Allergy shots: For hard-to-treat chronic hives, your healthcare provider may discuss monthly injections of drugs that block allergic reactions. People with severe allergies make too much IgE. These injections block your immune system from making IgE.
Anyone who has a severe acute allergic reaction could have life-threatening swelling of the airways — your throat and lungs. This condition is known as anaphylaxis. It can potentially close off the airways, resulting in death.
Anaphylaxis is often triggered by a severe allergic reaction to a certain food, like peanuts and tree nuts, or to a bee sting. If you have anaphylaxis, you need an immediate shot of epinephrine, such as injectable epinephrine (EpiPen® or AUVI-Q®).
Epinephrine opens airways, raises blood pressure and reduces hives and swelling. If you take epinephrine outside of a medical setting, you should go to the emergency room to be monitored. Symptoms of anaphylaxis can return as the epinephrine wears off.
Your healthcare provider can use the results of allergy tests to help you figure out which substances bring on acute hives. Once you know your triggers, you can avoid them. You may want to:
Some of these tips can also help with chronic hives.
It may not be possible to prevent chronic hives. Your provider may not be able to find exactly what causes them. They may also be a part of a bigger medical condition that affects your immune system.
For most people, hives don’t cause serious problems. Children often outgrow allergies that cause hives.
For some people, allergic reactions like angioedema can cause anaphylaxis — severe swelling of the airways and lungs. If you have this life-threatening condition, you should carry and know when and how to use injectable epinephrine (EpiPen®).
Hives can get better without treatment. Call your healthcare provider if you have:
If you develop hives, you might want to ask your healthcare provider these questions:
Hives usually go away after a few days to a few weeks. However, chronic hives can last much longer than that. It may take months, or longer, for chronic hives to go away.
COVID-19, like other infections, may be associated with skin rashes, including hives.
A note from Cleveland Clinic
Hives are your body’s way of responding to a substance (allergen) to which it’s sensitive. These reactions may be uncomfortable, but they’re often not serious. You may develop hives alone, hives with swelling, or just swelling. Most of the time, these reactions go away in a day or two. If you’re prone to these reactions, talk to your healthcare provider about getting tested for causes. Once you know what triggers your allergies, you can take steps to avoid your triggers and treat reactions.
Chronic hives won’t go away in a few weeks. It may take much longer. Be sure to let your provider know if treatment isn’t working. Treatment can be effective even though you don’t know why you have chronic hives.
Last reviewed by a Cleveland Clinic medical professional on 10/14/2022.